Packaging and storage—
Preserve in well-closed containers,protected from light and from excessive heat.
Identification—
Solution—
Prepare the test solution as follows.Suspend a quantity of Capsule contents,equivalent to about 200mg of rifabutin,in 20mLof methanol,sonicate for about 5minutes,and filter through a 0.5-µm or finer porosity filter.Dilute a portion of the filtrate quantitatively,and stepwise if necessary,with methanol to obtain a solution having a concentration of about 20µg per mL.Prepare a Standard solution by dissolving a quantity of
USP Rifabutin RSin methanol,with the aid of sonication,to obtain a solution having a concentration of about 20µg per mL,and filter through a 0.5-µm or finer porosity filter.
Medium:
methanol.
B:
The retention time of the major peak in the chromatogram of the
Assay preparationcorresponds to that in the chromatogram of the
Standard preparationobtained as directed in the
Assay.
Dissolution—
Medium:
0.01Nhydrochloric acid;900mL.
Apparatus 1:
100rpm.
Time:
45minutes.
Procedure—
Determine the amount of C
46H
62N
4O
11dissolved from UVabsorbances at the wavelength of maximum absorbance at about 280nm of filtered portions of the solution under test,suitably diluted with
Dissolution Medium,in comparison with a Standard solution having a known concentration of
USP Rifabutin RSin the same medium,taking into account its designated potency.
Tolerances—
Not less than 75%(Q)of the labeled amount of C46H62N4O11is dissolved in 45minutes.
Chromatographic purity—
Using the chromatogram of the
Assay preparationobtained as directed in the
Assay,calculate the percentage of impurities by the formula:
100(ri/rS),
in which
riis the response of an individual impurity and
rSis the sum of the responses of all peaks:any impurity peak detected at a retention time of about 0.5,0.6,0.8,or 1.4relative to the retention time of the rifabutin peak does not exceed 1.0%,not more than 0.5%of any other impurity is detected,and the total of all impurity peaks is not more than 4.5%.
Assay—
0.1M Monobasic potassium phosphate,Mobile phase,Standard preparation,Resolution solution,andChromatographic system—
Proceed as directed in the
Assayunder
Rifabutin.
Assay preparation—
Remove as completely as possible the contents of not less than 20Capsules,weigh accurately,and determine the average weight of the Capsule contents.Transfer an accurately weighed portion of the powder,equivalent to about 25mg of rifabutin,to a 50-mLvolumetric flask.Add 5mLof acetonitrile,dilute with Mobile phaseto volume,and mix.Filter through a 0.5-µm or finer porosity filter,and use the filtrate as the Assay preparation.
Procedure—
Proceed as directed for
Procedurein the
Assayunder
Rifabutin.Calculate the quantity,in mg,of C
46H
62N
4O
11in the portion of Capsules taken by the formula:
0.05CP(rU/rS),
in which the terms are as defined therein.